In the past, if you wanted to set up a Mac OS X-based server, you bought a separate DVD with an expensive license. In the case of Snow Leopard Server, that license was $499 for an unlimited number of users. Now, it appears that Lion Server is going to be a $49.99 set of apps that you'll purchase through the Mac App Store. This is a bit different from what we heard back in February, when Apple's PR department was touting that Lion Server would be bundled for free with every copy of Lion.
For those who are currently running the latest version of Mac OS X Server 1